The present invention relates to a method for in situ sampling and monitoring of a fluid flowing in a flow path. Furthermore the invention relates to an apparatus for in situ sampling and monitoring of a fluid flowing in a flow path.
The present invention may be utilized for sampling and analyzing/monitoring the condition of any kind of fluid, but may be especially suitable for analysis of particulates in a flowing fluid. The term monitoring will be used in the following, this term is meant also to include analyzing.
Analysis of debris particles in lubricating oil is a well-known method of monitoring the condition of oil wetted machinery. Particulate monitoring is also an important maintenance procedure for hydraulic systems. One commonly used method for performing the analysis is to withdraw a sample of fluid from the equipment manually and physically transport it to a laboratory for analysis. Once at the laboratory, various tests are performed, including particle counting and microscopic analysis of debris particles. Various methods are used for sample preparation for microscope analysis, including centrifugal separation, filterpatch and ferroaraphy. Once prepared, the samples are examined by a human expert and machine condition at the time the sample was taken is identified by subjective evaluation of the sample.
While this procedure is effective in some circumstances, it has deficiencies that reduce its effectiveness and raise its cost in many applications. Among the deficiencies are the long delay from drawing of the sample to receipt of analysis report, the need for sample preparation, the subjective evaluation of samples and the inherent inaccuracy of sampling as it is currently done from drain ports or sumps. In addition, the mere need for drawing a sample manually contributes to the maintenance workload and expense. In addition, it can often miss transient debris production that can be indicative of certain mechanical malfunctions.
Some of these deficiencies are addressed in known technologies. The inaccuracy of sampling is addressed with the on line fluid sampler in NO 171430 in which particles from the fall flow are captured in a sample bottle for transport and analysis.
Sample preparation and subjective evaluation are addressed in LaserNet Fines (LNF) by NRL and in U.S. Pat. No. 5,572,320 in which particles from a sample bottle are analyzed and classified automatically with computer classifiers, and quantitative measures of debris characteristics based on size and shape distributions are produced for evaluation of machine condition. LaserNet Fines also address the deficiency of long delay times between sample draw and report by being installed on site (or on ship or platform, depending on the circumstances).
LaserNetFines is a technology for identification of mechanical wear in oil-wetted machinery, but could also be used to survey the conditions of other kinds of fluid: LaserNetFines determines fault type and severity by measurement of size distribution, concentration, rate of production and shape characteristics of wear particles. It also detects and measures free water and fiber content and is applicable for cleanliness determination in hydraulic systems. The LaserNet Fines technology is compatible with implementation as a benchtop bottle sample analyzer or with on line operation for particle analysis without drawing a sample. To data LaserNet Fines has been implemented for mechanical wear and hydraulic monitoring as a bottle sampler.
Accurate sampling of the particulate content of the circulating fluid is vital to effective mechanical-wear or hydraulic-contamination monitoring. Inaccuracies associated with sampling through drain ports or other diverted flow—paths can easily lead to erratic trending results. In NO 171430 a full flow on-line sampler is introduced to provide accurate bottle sampling of the particles in the full flow of an oil system.
Neither of these technologies alone address the deficiency of the requirement of manually drawn samples with their accompanying expense and demand on workload. However, these publications provide the basis for the current invention; the complete document of NO 171430, the complete document of U.S. Pat. No. 5,572,320 and publication on LNF “On Line Operation of LaserNet Fines With Accurate Sampling”, Reintjes et al, should therefore be considered included as a whole in this current patent application.
The present invention combines in one embodiment a monitor system such as the LaserNet Fines with the fluid sampler in NO 171430 for accurate particle monitoring or any other monitoring of the fluid. LaserNet Fines can be operated on line on a laboratory flow loop. Particle counting and imaging results can be utilized for a variety of flow conditions. On line results are compared to bottle sample results for the same conditions.
The new aspects of this invention are the method and apparatus of obtaining simultaneously automatic on line reliable sampling of debris particles in fluid systems and automatic quantitative assessment of equipment condition through analysis of size and shape characteristics of the particles. Prior art outside of the two technologies included here suffer from inaccuracies in manually drawn samples originating in non-repeatable aspects of sampling, and from non-quantitative assessment of debris particles. Existing on line debris monitors that count and size particles cannot identify the type of mechanical fault responsible for the wear, and therefore cannot address the severity of the problem. The combination of the fluid sampler in NO 171430 and the LaserNet Fines debris monitor that the full power of on line sampling and debris analysis is realized. The invention covers method and apparatus for obtaining debris analysis based on size and shape characteristics with automatic on line operation and transmission of the analysis data to a remote site.
One object of this invention is to address the deficiency of the long delay and expense due to manual sample extraction and transport with method and apparatus by combining the sampling procedure in NO 171 430 with a monitor system such as the LNF in a manner that allows on line-automatic monitoring, eliminating the need for manual sampling and sample preparation for analysis.
It is a second object of this invention to provide for transmission of the analysis carried out in the monitor system, to a remote site, eliminating the need for travel to the equipment for data retrieval.